This invention relates to the production of synthetic fibers and it is particularly concerned with that phase of fiber production which involves the formation of tow just prior to crimping the fibers.
It is well established in the art that crimping of continuous-filament tows in stuffing box crimpers poses special problems. In order to impart uniform crimp, it is necessary to treat each filament in the tow the same and to treat each increment of length the same as another. To treat each filament and each increment of length the same in passing through a stuffing box crimper it is necessary to precisely control the width of the tow to prevent uneven filling which causes extreme pressures on the filaments and high friction between filaments and the crimper that damage filaments. Efforts toward this ideal have taken the form of stuffing rolls modification intended to adapt to the tow characteristics, as exemplified by the McCaskill U.S. Pat. No. 3,255,507 as well as adjustments in the configuration of the tow being fed to the stuffing rolls such as illustrated by the Resor U.S. Pat. No. 3,145,429, the Chadwick U.S. Pat. No. 3,231,958, the Tarbell U.S. Pat. No. 3,248,103 and the Roeder et al. U.S. Pat. No. 3,277,537. The McCaskill patent adapts the shape of the crimper roll faces to the somewhat oval cross-section of tow being fed to them. The Resor patent teaches the use of concave and uniform-diameter rolls for shaping individual bundles of wash-drawn tows and directing them to a usable, stacked arrangement for crimping. The Chadwick patent offers an alternative to the McCaskill solution in which means are provided for folding over the feathered edges to result in a uniform crimper feed. The Tarbell patent teaches an improved use of pins for stacking, which shapes and narrows the ropes by means including twice rotating them 90.degree.. The Roeder et al. patent teaches the importance of maintaining the rope through a minimum distance at narrower configuration; this prevents "spring back" to the initial width after passing the guide.
However, none of the above-noted references are capable of varying the width of th rope in both a widening and narrowing mode by simply adjusting its angular position with respect to the rope.